Reconciliation of Differences from U.S. Federal Statutory Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Expenses [Line Items]
Pretax book income	$ 185,417	$ 163,311	$ 98,462
Federal tax expense at 35% statutory rate	64,896	57,159	34,462
State and local income taxes	7,145	6,190	4,808
Benefit of domestic production deduction	(5,065)	(5,255)	(2,010)
Other	(992)	928	272
Total consolidated expense	$ 65,984	$ 59,022	$ 37,532